The most popular clown costumes, according to an informal poll of retailers, are Pennywise, from Stephen King’s “It” and “Twisty” from “American Horror Story: Freak Show.”

Over the past few months, children and adults have been scared enough to report the incidents to the police, including on Thursday when a knife-wielding clown chased a teenager through a New York City subway.

The clown fascination is now turning into retail gold.

“We expect to run out of [clown costumes] earlier than usual this year,”said Sharon Laurent, owner of Nightmarefactory.com, who noted that she had already sold out of 15 percent of her clown inventory.

At HalloweenCostumes.com, searches for clown costumes on are up 50 percent and sales of scary clown costumes are up 40 percent from a year ago, according to chief marketing officer Mark Bietz.